Solids separator

ABSTRACT

A solids removal device for use in the treatment of water and wastewater includes a final settling zone for removal of lightweight particles. The final settling zone comprises a liquid-carrying conduit defining a path for the upward flow of liquid and encloses settling plates dividing the conduit into flow spaces of upwardly increasing cross-sectional area and providing impingement and conglomeration surfaces for the accumulation and downward flow of solids.

llnited States atent Zuckerman et al.

[151 3,635,346 [451 ,lan.18,1972

[54] SOLIDS SEPARATOR [72] Inventors: Mathew M. Zuckerman, Yonkers; AlanH.

M0101, New York, both of NY.

[73] Assignee: Envirotech Corporation, Palo Alto, Calif.

[22] Filed: Feb. 24, 1970 211 App]. No.: 13,641

[52] US. Cl ..210/208, 210/521 [5|] Int.Cl ..B0ld 21/16 [58] FieldoISearch ..210/84, 521,522,208,311

[56] References Cited UNITED STATES PATENTS 1,020,013 3/1912 Arbuckle..210/521 1,030,271 6/1912 Arbuckle ..210/521 2,425,371 8/1947 Green..210/208 X 3,482,694 12/1969 Rice et a1. .....2l0/84 X 2,509,933 5/1950Lind ..210/522 X Primary ExaminerJohn Adee Attorney-Richard F.Bojanowski and Robert R. Finch [5 7] ABSTRACT A solids removal devicefor use in the treatment of water and wastewater includes a finalsettling zone for removal of lightweight particles. The final settlingzone comprises a liquid-carrying conduit defining a path for the upwardflow of liquid and encloses settling plates dividing the conduit intoflow spaces of upwardly increasing cross-sectional area and providingimpingement and conglomeration surfaces for the accumulation anddownward flow of solids.

7 Claims, 2 Drawing Figures sou s sammroa This invention relatesgenerally to apparatus for the separation of solid matter from liquidsand more specifically to improved solids removal apparatus for use inprocessing water and/or wastewater.

The production of high-quality water from wastewater requires a highdegree of removal of soluble and suspended material. In accordance withpresent treatment practices, conventional wastewater facilities removesuspended material continuously from wastewater by sedimentation,generally in tanks designed to provide sufficient time to permitsuspended material to settle to the tank bottom. The settled solidmaterial (commonly referred to as sludge") can be continuously orintermittently withdrawn. This basic settling procedure is relativelyinefficient in removing colloidal material and various techniques havebeen developed to improve this aspect of wastewater treatment.

. In accordance with one such improvement used where highquality wateris required, the removal of colloidal solids is aided by the addition ofcoagulating chemicals which foster development of larger, denserparticles from smaller particles and hence speed sedimentation. Anexemplary coagulation technique involves the addition of lime or saltsof aluminum or iron to wastewater followed by slow mixing of thewastewaterchemical solution so that clusters of particles (referred toas flocs") develop and grow in size and weight for more efficientsettling and removal.

One improvement in the removal of solid material from wastewater is thesolids contact" method wherein wastewater is continuously passed througha vertical settling tank containing previously settled materials. Thedirection of flow is from the lower end of the tank to the upper end andthe upward flow velocity is smaller than the settling velocity of thesolid material in the wastewater which is removed. While the liquidflows upward the previously settled material forms a layer of sludge(called a sludge blanket") at the lower end of the tank. Once theprocess gets underway, the sludge blanket acts as a filter andnucleating agent throughwhich the wastewater stream must pass. Solidmaterial in the wastewater tends to adhere to the sludge blanket and isthus removed. Sludge is drawn off from the sludge blanket for reuse ordisposal at a controlled rate so as to maintain the density and heightof the sludge blanket for efficient solids removal.

Various devices for removing suspended and colloidal solids fromwastewater according to this solids contact technique are currentlyavailable. Some of these devices which combine several process steps ina single piece of equipment are conventionally referred to as solidscontractors. While solids contactors are among the most effectivesedimentation devices available, they do not remove very light particleswhich are not filtered by the sludge blanket and which do not have asufficient settling velocity to reach the sludge blanket against theupward velocity of the liquid. Such particles are carried over in theoutput water reducing the output water quality.

In an attempt to improve the solids removal effectiveness, several suchdevices are now provided with regions of increasing cross-sectional areain the settling tank to decrease the upward velocity of the wastewaterrising through the tank. The decrease in flow velocity is proportionalto the increase in cross-sectional area in an obvious manner. Since thedegree of removal of any settleable particle is proportional to thedifference between the upward velocity of the liquid stream and thesettling velocity of the particles, these devices tend to remove more ofthe lighter particles than conventional devices. However, removal ofsuch light particles in these devices occurs only when the particlessettle to the sludge blanket. To reach this layer, these particles musttraverse a long settling path from the increased diameter region to thesludge blanket. These particles are often not removed due to localizedturbulent upsets which occur during the long travel time and are thusfrequently passed through the solids contactor.

It is a primary object of the present invention to remove settleablematerial from wastewater more effectively than has heretofore beenpossible and in a manner that will permit the removal of very small,lightweight particles. A related object of the present invention is toprovide a solids contactor in which lightweight particles need onlytraverse a short settling path to places of removal and in whichlocalized turbulences and flow upsets will be minimized so that solidscarryover will be reduced.

In accomplishing these and other objects in accordance with the presentinvention, a solids contactor having a vertical settling chamber isprovided with a final settling zone adjacent the upper end of thesettling chamber including a plurality of inverted frustoconicalsettling plates of increasing diameter arranged one within another anddefining annular conduits of upwardly increasing cross-sectional areatherebetween. The settling plates provide impingement surfaces for theaccumulation and eventual downward flow of these agglomeratedlightweight particles which have not been previously removed.

Further objects, features and advantages of the present invention willbe more fully appreciated by reference to the following detaileddescription of a presently preferred, but nonetheless illustrativeembodiment in accordance with the present invention, reference beingmade to the attached figures wherein:

FIG. 1 is a cross-sectional view of a solids contactor in accordancewith the present invention; and

FIG. 2 is a fractional view of the output section of the solidscontactor.

Referring to the drawings, the solids contactor 8 of FIG. 1 is adaptedto remove nonsoluble material including settleable colloidal andsupercolloidal material from water or wastewater in accordance with animproved solids contact sequence. The contactor comprises a chassis 10supported from beneath by a support brace 12 and enclosing a pluralityof internal wall sections which divide the contactor into variouswastewater treatment chambers and define a flow path therebetween. Ineach chamber, one aspect of the solids contact process is carried out.It is to be understood that the flow of wastewater through contactor 8is continuous and that each chamber operates on the liquid as liquidpasses through it.

wastewater is introduced into contactor 8 through a wastewater inputtube 14 which terminates at its lower end within an open or coveredrapid mixing chamber 16 defined by a inverted frustoconical wall 18supported by braces 20. Chamber [6 may also receive chemicals to aidcoagulation through a chemical input tube 22 which extends parallel totube 14 and releases chemicals at the lower end of chamber 16. Chamber16 is provided with internal stirring paddles 24 mounted on a driveshaft 260 and driven by motor 28. Motor 28 may be any one of manyconventional drive motors well known in the art and is shown in FIG. 1in representational form only. Shaft 26a is'geared to rotate at arelatively rapid rate, creating substantial liquid turbulence in chamber16 and dispersing the chemical additives throughout the wastewater.

Liquid exits chamber 16 by flowing upwardly over the upper lip of wall18 and downwardly through an annular channel 32 external to wall 18 andinternal to support wall 30.

Since it is important to maintain a unifonn balance flow throughout thepresent process as will be described hereinafter, the upper lip of wall18 should be maintained in a substantially horizontal position andpreferably provided with V-notches so that water overflows chamber 16uniformly about its circumference.

From rapid mixing chamber 16 the wastewater-chemical solution entersflocculation chamber 34 defined by cylindrical wall 36 positionedinternal to and coaxial with chassis 10. Chamber 34 encloses a secondplurality of paddle arms 38 mounted on drive shaft 26b to mix the liquidin chamber 34 relatively slowly as compared to chamber 16. Shafts 26aand 27b may comprise a single shaft so that paddles 24 and 38 rotate atequal speeds as shown in FIG. I. In this embodiment, the dimensions ofthe paddles are selected so as to impart greater energy to the liquid inchamber 16 than in chamber 34 and to promote more rapid agitation inchamber 16. Also in this embodiment, paddle 24 has substantially moresurface area than paddles 38. Alternatively, shafts 26a and 26b may beseparate and driven by separate motors or by a single motor through agear box which permits the shafts to rotate at different speeds in whichcase paddles 24 and 38 could be of the same relative size.

In flocculation chamber 34, the wastewater-chemical mixture is slowlyagitated by paddles 38 permitting accumulations of solid material todevelop and grow in size and density. The chemical-mechanicalrelationship of flocculation is well known in the wastewater-processingart. Such flocculation induces the creation of relatively largeconglomerations of solid particles which will more easily be settled orfiltered out of the wastewater.

Flocculation chamber 34 opens downwardly and the wastewater flow travelsdownwardly out of the flocculation chamber, turns through an angle ofsubstantially 180 and travels upwardly into settling chamber 44 definedby cylindrical wall 36 and chassis 10. Chamber 44 is the primarysettling and solids-contacting chamber wherein solid material settlesdownwardly while the liquid flow travels upwardly. The result of thisprocess is the development of a sludge blanket 46 comprising a densearea of solid particles previously settled from the wastewater stream.Sludge blanket 46, as it accumulates, acts as a filter and nucleatingagent in accordance with the well-known solids contact procedure wherebyas wastewater exiting chamber 34 passes through sludge blanket 46 thesolid particles carried therein tent to be filtered and adhere to thesolid material in blanket 46 and are removed from the wastewater. Sludgeblanket 46 thus tends to grow in size as the process proceeds. Inaccordance with conventional practice, the material in sludge blanket 46is drawn off through a duct 48 at the lower end of contactor 8. Themajor portion of the sludge is disposed of by various means known tothose skilled in the art. A minor portion of the sludge may be removedthrough duct 48 or other appropriately positioned ducts to bereintroduced into the wastewater in input tube 14 to accelerate thesedimentation process in accordance with techniques well known in theart.

The lower end of contactor 8 includes a rotary rake 50 which is securedto and rotates with shaft 26b to scrape the side of the conical lowersection of contactor 8. Rake S includes upwardly projecting mixing arms51 which move through the sludge and act to thicken it prior to removal.

in a preferred method of operation, the upper end of sludge blanket 46is maintained within the vertical settling chamber 44 or the firstexpansion area by intermittent or continuous withdrawal of sludgethrough takeoff duct 48 or optional drawoff ducts.

As the wastewater rises through chamber 44 it enters a first expansionarea 53 formed by exterior wall and interior wall 54 which anglesinwardly. Since the cross-sectional area of the annular flow space insection 53 is larger than the cross-sectional area of the annular flowspace in section 44, the upward velocity of the liquid decreases as itsflows upwardly through chamber 53. As the upward velocity decreases,lighter particles tend to settle out more readily since their settlingrate is proportional to the difference between the upward velocity ofthe liquid and the settling velocity of the particles. Expansion chamber53 thus aids settling of smaller lighter particles in the wastewater.Additionally, chamber 53 establishes a uniform radial velocitydistribution before the liquid passes into the final settling zone.

Above chamber 53 is the final settling zone generally designated 56which acts to remove small lightweight particles. The final settlingzone is bounded ,by the external wall 58 and internal wall and includesplurality of inverted frustoconical settling plates 60:: through 602supported by struts 62. Settling plates 60a-60e define flow paths ofannular cross section between adjacent plates for the upward flow ofliquid from chamber 53 to output weir 70 to be described hereinafter.

The annular flow spaces between adjacent pairs of settling plates aredimensioned such that the upflowing liquid is evenly distributed overthe entire flow area. Such distribution prevents local turbulences whichwould interfere with the settling process. To accomplish such evendistribution, the crosssectional area of the inlet to the annular flowspaces between plates 60a-60e are all equal. Since these annularchannels have different average diameters, the width of each flow space(the distance between adjacent plates) must be different for the innerplates than for the outer plates. A particular distance relationship isshown in FIG. 1. Further, the upper edge of each frustoconical plate islocated at an elevation below the surface of the contactor such that thecross-sectional area between the contactor top surface and the upperedge of the plate is equal to the total cross-sectional area of theinlets interior to the plate. The use of uniform inlet and outlet areaspermits a constant and steady flow state throughout the final settlingarea preventing local upsets and disturbances which would inhibitsettling.

It will be appreciated that the cross-sectional area of each annularflow space is greater at the upper end of the flow space than at thelower end and increases at a continuous rate from the lower end to theupper end. This increase occurs because the average diameter of theannular flow spaces at the lower end of the settling plates is smallerthan the average diameter of the annular flow spaces at the upper endand the plates 60a60e are parallel to one another. The velocity of theupflowing liquid thus decreases as the liquid flows upwardly through thefinal settling section. This progressive reduction in velocity furtheraids the settling of a lighter weight particle which has low settlingvelocities.

An additional advantage arises from the plate spacing which can be soarranged that any particle traveling in a vertical direction wouldimpinge on the under surface of a settling plate.

Settling plates 60a-60e provide a collection surface for lightweightsolid particles in the liquid stream which travel downwardly as theliquid flows upwardly until they impinge on the interior surface of asettling plate 6011-602. The solid material which accumulates on theinterior surface of the settling plates forms a flow layer of solidmaterial which travels downwardly by its own weight along the surface ofthe settling plates to the plate bottom and from the plate bottom inlarge clusters to the sludge blanket. Similarly, impingement andaccumulation on the bottom surface of the settling plate 60a-60 couldoccur directly for the lightweight particles which travel upwardly asthe liquid flows upwardly. This mass of concentrated suspended materialgenerally comprises the lightweight particles which would not have beenremoved has they been required to settle to the sludge blanketindividually. The dense globules of material which break away from theplates 60a60e settle rapidly to the sludge blanket where they areremoved in the manner described above.

Clarified liquid which flows outwardly from the upper end of settlingplates 6011-602 spills over the upper lip of circular weir 70 and intoannular channel 66 defined by weir 70 and the upper edge of sidewall 58.To insure a uniform flow about the circumference of weir 70, the weirincludes a series of V- notches 68 about its circumference. Theupflowing liquid flows out of V-notches 68 at a relatively uniform rateabout the circumference of the weir and into channel 66 where it isdrawn off by output tubes 72 located at equidistant points about thecircumference of the contactor. Additionally, weir 70 is maintained in asubstantially horizontal position to insure uniform flow.

When lime is the chemical addition the entire unit may be covered by atop plate 74 to reduce the entrance of atmospheric carbon dioxide whichwould form calcium carbonate floc at the surface of the contactor and becarried over into the effluent as suspended solids.

The final settling zone thus permits removal of light particles whichare not removed by conventional devices. Throughout the final settlingzone, the dynamic flow of liquid is maintained such that localturbulences and upsets are avoided and so that the system flow isrelatively uniform throughout the 360 circumference of the finalsettling zone.

It is to be understood that the above described arrangements are merelyexamples of the principles of'the present invention. Numerous otherembodiments will be obvious to those skilled in the art withoutdeparting from the spirit or scope of the invention.

What is claimed is:

ll. Apparatus for removing nonsoluble material from a liquid comprisinga conduit defining a flow path of upwardly increasing cross-sectionalarea for the upward flow of said liquid, said conduit enclosing aplurality of inverted frustoconical spacedapart settling plates whichextend out wardly from the center in a stepdown fashion and providing arelatively constant increasing vertical distance from the upper edge ofeach settling plate, said spaced-apart plates defining flow pathstherebetween of upwardly increasing cross-sectional area and forproviding impingement surfaces for the accumulation anddownward flow ofsaid nonsoluble material and wherein the cross section area of said flowpaths are substantially equal at their inlet ends, input means adjacentthe lower end of said conduit for directing liquid to said conduit, andoutput means adjacent the upper end of said conduit for directingclarified liquid away from said conduit.

2. Apparatus in accordance with claim 1 wherein the settling plates aresubstantially parallel to each other and thereby provide a substantiallyuniform increase in the cross-sectional areas of said subflow paths fromthe lower end of said conduit to the upper end thereof.

3. Apparatus in accordance with claim 2 wherein the spaced-apart,substantially parallel settling plates are inverted frustoconical platesof increasing diameter arranged one within another.

4. Apparatus for removing settleable material from a liquid comprising achassis having a primary liquid inlet and a liquid outlet and defining aflow path for liquid therebetween, said flow path including acylindrical flocculation chamber communicating at its upper end withsaid inlet, an annular settling chamber external to said flocculationchamber and communicating at its lower end with the lower end of saidflocculation chamber whereby said flow path emanates in a downwardlydirection from said flocculation chamber, turns outwardly and upwardlythrough an angle of substantially into said annular settling chamber,and a final settling zone including a plurality ofinverted'trustoconical settling plates arranged one within another inoutward radially stepdown arrangement and in parallel relationship toeach other to define therebetween substantially concentric liquid flowpaths having substantially equal cross-sectional areas at their inletends and upwardly increasing cross-sectional area, said stepdownarrangement providing a relatively constant increasing vertical distancefrom the upper edge of each settling plate and said settling plates attheir lower ends communicating with the upper end of said annularsettling chamber and at their upper ends with said outlet.

5. Apparatus in accordance with claim 4 wherein said annular settlingchamber includes a section of upwardly increasing cross-sectional areaimmediately preceding said final settling area.

6. Apparatus in accordance with claim 4 further including means locatedbelow said settling chamber and said flocculation chamber for receivingaccumulations of said settleable material and for removing saidaccumulations at a controlled rate.

7. Apparatus in accordance with claim 4 wherein said flow path furtherincludes a rapid mixing chamber communicating at its input end with saidprimary liquid inlet and at its output end with said flocculationchamber, said rapid mixing chamber including a secondary liquid inletfor the addition of chemicals to said liquid.

1. Apparatus for removing nonsoluble material from a liquid comprising aconduit defining a flow path of upwardly increasing cross-sectional areafor the upward flow of said liquid, said conduit enclosing a pluralityof inverted frustoconical spacedapart settling plates which extendoutwardly from the center in a stepdown fashion and providing arelatively constant increasing vertical distance from the upper edge ofeach settling plate, said spaced-apart plates defining flow pathstherebetween of upwardly increasing cross-sectional area and forproviding impingement surfaces for the accumulation and downward flow ofsaid nonsoluble material and wherein the cross section area of said flowpaths are substantially equal at their inlet ends, input means adjacentthe lower end of said conduit for directing liquid to said conduit, andoutput means adjacent the upper end of said conduit for directingclarified liquid away from said conduit.
 2. Apparatus in accordance withclaim 1 wherein the settling plates are substantially parallel to eachother and thereby provide a substantially uniform increase in thecross-sectional areas of said subflow paths from the lower end of saidconduit to the upper end thereof.
 3. Apparatus in accordance with claim2 wherein the spaced-apart, substantially parallel settling plates areinverted frustoconical plates of increasing diameter arranged one withinanother.
 4. ApparAtus for removing settleable material from a liquidcomprising a chassis having a primary liquid inlet and a liquid outletand defining a flow path for liquid therebetween, said flow pathincluding a cylindrical flocculation chamber communicating at its upperend with said inlet, an annular settling chamber external to saidflocculation chamber and communicating at its lower end with the lowerend of said flocculation chamber whereby said flow path emanates in adownwardly direction from said flocculation chamber, turns outwardly andupwardly through an angle of substantially 180* into said annularsettling chamber, and a final settling zone including a plurality ofinverted frustoconical settling plates arranged one within another inoutward radially stepdown arrangement and in parallel relationship toeach other to define therebetween substantially concentric liquid flowpaths having substantially equal cross-sectional areas at their inletends and upwardly increasing cross-sectional area, said stepdownarrangement providing a relatively constant increasing vertical distancefrom the upper edge of each settling plate and said settling plates attheir lower ends communicating with the upper end of said annularsettling chamber and at their upper ends with said outlet.
 5. Apparatusin accordance with claim 4 wherein said annular settling chamberincludes a section of upwardly increasing cross-sectional areaimmediately preceding said final settling area.
 6. Apparatus inaccordance with claim 4 further including means located below saidsettling chamber and said flocculation chamber for receivingaccumulations of said settleable material and for removing saidaccumulations at a controlled rate.
 7. Apparatus in accordance withclaim 4 wherein said flow path further includes a rapid mixing chambercommunicating at its input end with said primary liquid inlet and at itsoutput end with said flocculation chamber, said rapid mixing chamberincluding a secondary liquid inlet for the addition of chemicals to saidliquid.